This invention relates to a resin composition and a container made of the resin composition. The resin composition is one that is a suitable component of a container which contains items of skin care, hair care, other cosmetics, foods, and other items.
One example of the prior art uses a mono-layer or a multi-layer polyolefin-type resin as a component of hollow containers. The polyolefin-type resin exhibits good extruding capability and adhesion capability in the part where the container is pinched off. Another example of the prior art uses a polyolefin-type resin, which has good extruding capability and heat sealing capability, as a component of an inside layer of tube shaped containers. Prior art containers which have a multi-layer structure use a polyolefin-type resin for the inner-most layer. When the polyolefin-type resin is used for the inner-most layer, it increases the pinch off adhesion and heat sealing capability of the container. Examples of the polyolefin-type resin include high density polyethylene, low density polyethylene, linear low density polyethylene, random co-polypropylene, and block copolypropylene.
The above-recited prior art polyolefin-type resins do not provide a suitable gas barrier or oil resistance. To overcome this drawback, Japanese Patent Publication Nos. 43074/1976, 23792/1981, and 15532/1982, and Japanese Laid-open Patent No. 49939/1985 attempt to provide a barrier resin such as ethylene vinyl alcohol copolymer and nylons to prevent the invasion of oxygen gas from the environment and the infiltration of oily components.
Prior art containers which contain a polyolefin-type resin have problems when carrying items of skin care, hair care, other cosmetics, and foods which have oily components. These oily components include various kinds of animal oil and vegetable oil and their ester interchange derivatives, synthetic oils, like isoparafin, and silicon oil. These oily components infiltrate into the resin of the polyolefin, which is a component of the containers. When the container has a mono-layer wall of a polyolefin-type resin, the oily components bleed out the surface of the container. When the container has a multi-layer structure with a barrier resin in the middle layers and the inner-most layer is a polyolefin-type resin, the inner-most layer absorbs the oily components and swells. As a result, the container is deformed by the bimetallic effects. Most items carried in the above-mentioned container are 50-60% oily components. However, this drawback is a greater problem when the item carried in the container is 80-90% oily components.
In recent years, blending flavors such as menthol and mints and other aromatics, vitamin E, and various extracts has become popular. These components also infiltrate or permeate into the inner layer materials of the containers or they are absorbed by the inner layer materials, and thus, reduce the amount of those components in the item carried in the container. Therefore, the effect of blending decreases and the expected effect is lost.
Japanese Patent Publication No. 26008/1985 and Japanese Laid-open Patent No. 219646/1990 try to solve the above-mentioned problems using an ethylene vinyl alcohol copolymer for the inner-most layer of a tube-shaped container. Japanese Patent Publication Nos. 84877/1976, 92880/1976, and 53817/1987, and Japanese Laid-open Patent No. 50260/1988 try to solve the above-mentioned problems using nylon or polyethyleneterphthalate resin.
The above-recited prior art does prevent the container from absorbing the oil. However, the materials, which the above-mentioned prior art uses to make the container, are inferior in pinch off adhesion capability and heat sealing capability.
An additional drawback in using ethylene vinyl alcohol copolymer, nylon or polyethyleneterephthalate resin for the inner-most layer of the container is that the container lacks flexibility. Thus, characteristics of a container made of a polyolefin type resin, such as flexibility and ease of squeezing the contents out, cannot be expected. This disadvantage in turn leads to a decrease in the value of the container by almost half. Additionally, advantages of using a plastic container, such as its resistance to breaking and the ease of squeezing or pressing out the contents of a tubular container, are lost, and thus, the value of the container is cut by half.
When a container is made of multiple layers of nylons, polyethyleneterephthalate resin, and polyolefin-type resins, the manufacturing process is difficult because the optimum processing temperatures of each layer are different from the others. Additionally, when the production process uses force to bring the multiple layers together the container is deformed because of the differences of the coefficients of contraction of each layer.
See U.S. Pat. No. 4381337 which discloses a blended resin selected from a polyester resin having a high Tg and a polyester resin having a low Tg.
See also, U.S. Pat. No. 3382295 which discloses a blended resin selected from an amorphous resin with a high Tg value and one selected from an amorphous polyester resin with a low Tg value.